ToolVet
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Amm Invariant Monitor

by mev.halowerk.com in Developer tools

x402 APIPassing, checked 4 h ago

AMM Invariant Monitor analyses only the evidence supplied by the caller. It does not claim to query a chain, identify a legal status or replace an independent audit. Missing signals lower confidence and are listed explicitly; every classification includes the exact thresholds used.

POST
https://mev.halowerk.com/v1/amm-invariant-monitor
Price
$0.001
per call in USDC
Uptime
100%
last 30 days
Response time
198 ms
273 ms slowest 5%
Last check
Passed
4 h ago, next any minute now

Run a free test callHow to call it

Reliability

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Status and outage history · Atom feed · Watch with other listings

How to call it

POST https://mev.halowerk.com/v1/amm-invariant-monitor

Each call costs $0.001 in USDC on Base, paid with the request over x402.

Run a free test callOne unpaid request, the way an agent sends it. You see the payment challenge it gets back. Nothing is charged.

Example request

From the listing.

POST https://mev.halowerk.com/v1/amm-invariant-monitor
content-type: application/json

{
  "context": {
    "environment": "production"
  },
  "evidence": [
    {
      "metric": "invariant_deviation_pct",
      "source": "caller-observation",
      "timestamp": "2026-09-03T10:00:00Z",
      "value": 1
    },
    {
      "metric": "reserve_mismatch_pct",
      "source": "caller-observation",
      "timestamp": "2026-09-03T10:00:00Z",
      "value": 1
    },
    {
      "metric": "unexplained_delta_count",
      "source": "caller-observation",
      "timestamp": "2026-09-03T10:00:00Z",
      "value": 1
    }
  ],
  "strict": true,
  "subject": "amm-invariant-monitor-sample"
}

Parameters

ParameterTypeRequiredDescription
contextobjectNoOptional non-secret labels returned unchanged for correlation.
evidencearray of objectYesCaller-supplied observations. Repeated metrics form a time series; the newest timestamp is assessed.
strictbooleanNoReject unless all documented metrics are supplied. Default: false.
subjectstringYesAddress, transaction, protocol, asset, proposal or other subject being assessed.

Example response

The listing has no example response.

Call it from code

The curl command shows the payment challenge. The JavaScript and Python versions pay and call, and never pay more than $0.001.

curl: see the payment challenge
# bash or zsh: see the payment challenge. Nothing is charged.
curl -sS -g -i -X POST 'https://mev.halowerk.com/v1/amm-invariant-monitor' \
  -H 'content-type: application/json' \
  --data-raw '{"context":{"environment":"production"},"evidence":[{"metric":"invariant_deviation_pct","source":"caller-observation","timestamp":"2026-09-03T10:00:00Z","value":1},{"metric":"reserve_mismatch_pct","source":"caller-observation","timestamp":"2026-09-03T10:00:00Z","value":1},{"metric":"unexplained_delta_count","source":"caller-observation","timestamp":"2026-09-03T10:00:00Z","value":1}],"strict":true,"subject":"amm-invariant-monitor-sample"}'

# x402 v2 sends the challenge base64-encoded in the PAYMENT-REQUIRED header (v1 sends it in the body).
# To read the header:
curl -sS -g -o /dev/null -D - -X POST 'https://mev.halowerk.com/v1/amm-invariant-monitor' \
  -H 'content-type: application/json' \
  --data-raw '{"context":{"environment":"production"},"evidence":[{"metric":"invariant_deviation_pct","source":"caller-observation","timestamp":"2026-09-03T10:00:00Z","value":1},{"metric":"reserve_mismatch_pct","source":"caller-observation","timestamp":"2026-09-03T10:00:00Z","value":1},{"metric":"unexplained_delta_count","source":"caller-observation","timestamp":"2026-09-03T10:00:00Z","value":1}],"strict":true,"subject":"amm-invariant-monitor-sample"}' \
  | grep -i '^payment-required:' | cut -d' ' -f2 | tr -d '\r' | base64 --decode
JavaScript: pay and call
// npm i @x402/fetch @x402/evm viem
import { wrapFetchWithPayment, x402Client } from "@x402/fetch";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";

// Pays at most $0.001 per call.
const client = new x402Client().setSpendControls({ maxAmountPerPayment: "$0.001" });
registerExactEvmScheme(client, { signer: privateKeyToAccount(process.env.EVM_PRIVATE_KEY) });
const pay = wrapFetchWithPayment(fetch, client);

// Not sure it's safe to pay? ToolVet checks it first for $0.005. Pay for that from a separate
// client: this one is capped at $0.001 per payment. GET https://toolvet.app/api/v1/check?url=https%3A%2F%2Fmev.halowerk.com%2Fv1%2Famm-invariant-monitor&method=POST
const res = await pay("https://mev.halowerk.com/v1/amm-invariant-monitor", {
  method: "POST",
  headers: { "content-type": "application/json" },
  body: JSON.stringify({
    "context": {
      "environment": "production"
    },
    "evidence": [
      {
        "metric": "invariant_deviation_pct",
        "source": "caller-observation",
        "timestamp": "2026-09-03T10:00:00Z",
        "value": 1
      },
      {
        "metric": "reserve_mismatch_pct",
        "source": "caller-observation",
        "timestamp": "2026-09-03T10:00:00Z",
        "value": 1
      },
      {
        "metric": "unexplained_delta_count",
        "source": "caller-observation",
        "timestamp": "2026-09-03T10:00:00Z",
        "value": 1
      }
    ],
    "strict": true,
    "subject": "amm-invariant-monitor-sample"
  }),
});
console.log(res.status, await res.text());
Python: pay and call
# pip install "x402[requests,evm]"
import os
from eth_account import Account
from x402 import x402ClientSync
from x402.http.clients import x402_requests
from x402.mechanisms.evm import EthAccountSigner
from x402.mechanisms.evm.exact.register import register_exact_evm_client

# Pays at most $0.001 per call.
client = x402ClientSync().set_spend_controls({"max_amount_per_payment": "$0.001"})
register_exact_evm_client(client, EthAccountSigner(Account.from_key(os.environ["EVM_PRIVATE_KEY"])))

with x402_requests(client) as session:
    res = session.post(
        "https://mev.halowerk.com/v1/amm-invariant-monitor",
        json={
            "context": {
                "environment": "production",
            },
            "evidence": [
                {
                    "metric": "invariant_deviation_pct",
                    "source": "caller-observation",
                    "timestamp": "2026-09-03T10:00:00Z",
                    "value": 1,
                },
                {
                    "metric": "reserve_mismatch_pct",
                    "source": "caller-observation",
                    "timestamp": "2026-09-03T10:00:00Z",
                    "value": 1,
                },
                {
                    "metric": "unexplained_delta_count",
                    "source": "caller-observation",
                    "timestamp": "2026-09-03T10:00:00Z",
                    "value": 1,
                },
            ],
            "strict": True,
            "subject": "amm-invariant-monitor-sample",
        },
    )
    print(res.status_code, res.text)

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